TRA2981 - Traxxas Charger, EZ-Peak® Plus 4s, 8 amp, NiMH/LiPo with iD® Auto Battery Identification - Fast Eddie's RC Hobbies
Biggest batteries I've found to fit in the stock XRT battery tray are these HRB 9500mah 4s 120c packs. The Lectron pro 5200's the hobby sold me are way too small. These
Traxxas Velineon VXL-4S Brushless Electronic Speed Control #3465 - Hobby Time RC
Amazon.com: Socokin 4S Lipo Battery 14.8V 6500mAh 100C with TR Plug Soft Case for RC Car X-Maxx RC Boat RC Racing Truck Helicopter Airplane(2 Pack) : Toys & Games
Traxxas EZ-PEAK LIVE 2971 Charger with (2) 14.8v 4S 2890x Batteries X-MAXX 20334299307 | eBay